ansible: move the cross-host ports to host_vars, delete services_config.yml

The four ports were the only entries in services_config.yml with a real
justification: each is read twice, by the role that deploys the service on its
own box AND by a socket-proxy or Caddy play that runs on the EDGE host and
publishes it. A role default is invisible to that second play.

But the shape was wrong in two ways. The file had to be named in vars_files: by
30 plays - opt-in configuration that someone will eventually forget - and five
role defaults silently interpolated service_settings.*, so bitcoin_knots,
fulcrum, datum_gateway and mempool were not self-contained: using any of them
without that one vars_file entry broke it.

Each port now lives in host_vars/<owning box>/main.yml:

  host_vars/knots_box_local/main.yml    bitcoin_p2p_port, datum_gateway_api_port,
                                        datum_gateway_stratum_port
  host_vars/fulcrum_box_local/main.yml  fulcrum_ssl_port
  host_vars/mempool_box_local/main.yml  mempool_frontend_port

host_vars auto-loads and outranks role defaults, so the owning role picks the
value up with no vars_files at all, and the edge play reads the same single
definition as hostvars['<host>'].<name>. The role defaults keep the protocol
standard (8333, 50002, ...) so each role still works standalone, with the live
deployment's value in host_vars winning.

Also fixed a fourth copy of an inventory identity: the mempool Caddy play had
"mempool-box:{{ ... }}" hardcoded in the upstream. It now derives the host from
hostvars['mempool_box_local'].ansible_host, so inventory is the only place any
box's name is written down.

services_config.yml is deleted, with 25 more vars_files entries across 19
playbooks. Between this and the previous commit, 87 vars_files entries are gone
and every variable in the repo now comes from group_vars/all, host_vars,
inventory, a role default, or that service's own *_vars.yml.

Verification: an edge-host probe resolves all eight ports and hostnames to
byte-identical values to the ones services_config.yml used to supply. Each
owning host resolves its own port through host_vars. All 37 playbooks'
--list-tasks output is unchanged. The four edge plays that consume these values
all check-diff changed=0 - the socket-proxy and Caddy units on vipy are
byte-identical, which is the direct proof the rewiring landed on the same
values. fulcrum and datum-gateway check-diff exactly as before (ok=28/changed=1
and ok=15/changed=1, both the known timer re-arm).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ansible/roles/bitcoin_knots/defaults/main.yml

@@ -15,9 +15,11 @@ bitcoin_conf_dir: /etc/bitcoin
 
 # Network
 bitcoin_rpc_port: 8332
-# Shared with the socket-proxy play on the edge host, so it lives in
-# services_config.yml rather than only here.
-bitcoin_p2p_port: "{{ service_settings.bitcoin.p2p_port }}"
+# The edge host's socket-proxy/Caddy play needs this too, and a role default is
+# invisible outside this role. The authoritative value for the live deployment is
+# in host_vars/knots_box_local/main.yml, which outranks this; the value here is the
+# protocol standard, so the role still works standalone.
+bitcoin_p2p_port: 8333
 bitcoin_rpc_bind: "0.0.0.0"
 
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